Robert H. Loblay, Anne R. Swain:
The Role of Food Intolerance in Chronic Fatigue Syndrome,

in The Clinical and Scientific Basis of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome

B.M. Hyde, J. Goldstein, and P. Levine, Editors. 1992
The Nightingale Research Foundation: Ottawa. p. 521-538 Extract:

Although much attention has been paid in recent years to the adverse effects of food additives, naturally occurring food chemicals are a more insidious and more common cause of problems. Natural chemicals play a central role in the complex symbiotic relationship between animals and plants which has developed as a result of co-evolution. Plants are known to be capable of synthesizing an enormous range of substances important for their own survival and reproduction. Amongst these are a variety of anti-microbial and anti-parasitic agents, as well as chemicals which can modify the feeding behaviour of insects and higher animals. Not surprisingly, some of these substances can be toxic to humans if ingested in significant quantities.

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